Glossary of Terms

Speed of advance of a pipe jack or other trenchless installation through the ground, generally expressed as either millimetres per minute or metres per day.

ANNULAR FILLER

Material for grouting the annular space between the existing pipeline and the lining system.

AUGER BORING

Method of forming a bore, usually from a drive pit, by means of a rotating cutting head. Spoil is removed back to the drive pit by helically wound auger flights rotating in a steel casing. The equipment may have limited steering capability.

AUGER TBM

Tunnel boring machine (TBM) in which the excavated soil is removed to the drive shaft by auger flights passing through the product pipeline pushed in behind the TBM.

Principal module which is part of a shield machine as in microtunnelling or of a TBM. Two or more may be used, depending on the installation dimensions required and the presence of an articulated joint to facilitate steering.

CARRIER PIPE

Pipe to be rehabilitated by any trenchless rehabilitation method.

CASED BORE

Bore in which a pipe, usually a steel sleeve, is inserted simultaneously with the boring operation. Usually associated with auger boring or pipe jacking.

CASING

Pipe to support a bore. Usually not a product pipe.

CASING PIPE METHOD

Method in which a casing, generally steel, is pipe jacked into place, within which a product pipe is later inserted.

CAULKING

General term which, in trenchless technology, refers to methods by which joints may be closed within a pipeline or between lining segments.

CCTV

Closed circuit television used to carry out internal inspection and survey of pipelines.

CHEMICAL GROUTING

Method for the treatment of the ground around a shaft or pipeline, using non-cementitious compounds, in order to facilitate or make possible the installation of an underground structure.

CHEMICAL STABILISATION

Renovation method in which a length of pipeline between two access points is sealed by the introduction of one or more compounds in solution into the pipe and surrounding ground and, where appropriate, producing a chemical reaction. Such systems may perform a variety of functions such as the sealing of cracks and cavities, the provision of a new wall surface with improved hydraulic characteristics or ground stabilisation.

General term which, in trenchless technology, refers to the use of compressed air within a tunnel or shaft in order to balance ground water pressure and to prevent ingress into an excavation open to the atmosphere.

Method in which access is gained by excavation from ground level to the required level underground for the installation, maintenance or inspection of a pipe, conduit or cable. The excavation is then backfilled and the surface reinstated.

CONVENTIONAL TUNNELLING

Method of tunnel construction ranging from manual excavation to the use of self-propelled tunnel boring machines. Where a lining is required, bolted segmental rings are frequently used.

Steerable method for the installation of pipes, conduits and cables in a shallow arc using a surface launched drilling rig. In particular, the term applies to large scale crossings in which a fluid filled pilot bore is drilled without rotating the drill string, and this is then enlarged by a washover pipe and back reamer to the size required for the product pipe. The required deviation during pilot boring is provided by the positioning of a bent sub

Tool which cuts the ground at the head of a drill string, usually by mechanical means.

DRILL STRING/STEM

The total length of drill rods/pipe, bit, swivel joint etc. in a bore.

DRILLING FLUID/MUD

Mixture of water and, usually, bentonite or polymer continuously pumped to the cutting head or drill bit to facilitate the removal cuttings, stabilise the bore, cool the head and lubricate the passage of the product pipe. In suitable ground conditions water alone may be used.

DRIVE/ENTRY/SHAFT/PIT

Excavation from which trenchless technology equipment is launched for the installation or renovation of a pipeline, conduit or cable. It may incorporate a thrust wall to spread reaction loads to the ground.

DRY BORE

Method of creating a bore without the use of a drilling fluid. Usually associated with guided impact moling, but may also apply to some rotary methods.

Term commonly used in North America as an alternative to Impact Moling.

EARTH PRESSURE BALANCE (EPB) MACHINE

Type of microtunnelling machine in which mechanical pressure is applied to the material at the face and controlled to provide the correct counter-balance to earth pressure in order to prevent heave or subsidence. The term is usually employed where the pressure originates from the main jacking station in the drive shaft or to systems in which the primary counter-balance to the earth pressure is supplied by pressurised drilling fluid or slurry.

EARTH PRESSURE BALANCE (EPB) SHIELD

Mechanical tunnelling shield which utilises a full face to support the ground in front of the shield and usually employs an auger flight to extract the material in a controlled manner.

ENTRY/EXIT ANGLE

Angle to the ground surface at which the drill string enters or exits in forming the pilot bore in a directional drilling/guided drilling system.

EPB

Abbreviation for Earth Pressure Balance.

EXPANDER

A tool which enlarges a pilot bore during a pull-back operation by compression of the surrounding ground rather than by excavation. Sometimes used during a thrusting process as well as during pull-back.

Material comprising cementitious and steel elements to form a structural lining, which is either placed in situ in a man-entry size pipeline or tunnel, or is preformed into segments for later installation.

FLUID ASSISTED

Method of guided drilling using a combination of mechanical drilling and BORING/DRILLING pressurised fluid jets to provide the soil cutting action.

Device used to support or guide, first the shield and then the pipe within the drive shaft during a pipe jacking operation.

GUIDED AUGER BORING

Method of auger boring in which the guidance mechanism actuator is sited in the drive shaft. The term may also be applied to those auger boring systems with rudimentary articulation of the casing near the cutting head activated by the rods from the drive shaft.

Method for the installation of pipes, conduits and cables using a surface- launched drilling rig. A pilot bore is drilled using a rotating drill string and is then enlarged by a back reamer to the size required for the product pipe. The necessary deviation during the pilot boring is provided by a slanted face to the drill head, eccentric fluid jets or a combination of these, usually in conjunction with a locator.

Method of creating a bore using a pneumatic or hydraulic hammer within a casing, generally of torpedo shape. The term is usually associated with non- steered or limited steering devices without rigid attachment to the launch pit, relying upon the resistance of the ground for forward movement. During the operation the soil is displaced, not removed. An unsupported bore may be formed in suitable ground, or a pipe drawn in or pushed in behind the impact moling tool. Cables may also be drawn in.

As for drive pit but more usually associated with launching an impact moling or similar tool.

LEAD PIPE

The leading pipe designed to fit the rear of a jacking shield and over which the trailing end of the shield is fitted.

LINING WITH CLOSE-FIT PIPES

Method of lining with a continuous pipe for which the cross section is reduced to facilitate installation, and reverted after installation to provide a close fit to the existing pipe.

LINING WITH CONTINUOUS PIPE

Method of lining with a pipe made continuous for the length of the section to be renovated prior to insertion, and which has not been shaped to give a cross sectional diameter smaller than its final diameter after installation.

LINING WITH CURED-IN-PLACE PIPES

Method of lining with a flexible tube impregnated with a thermosetting resin which produces a pipe after resin cure.

LINING WITH DISCRETE PIPES

Method of lining with pipes shorter than the section to be renovated which are not jointed prior to insertion to form a continuous pipe, and which have not been shaped to give them a cross sectional diameter smaller than their final diameter after installation.

LINING WITH INSERTED HOSE

Method of lining with a loose fit reinforced hose to provide a pipe lining such that fluids may be conveyed under pressure.

LINING WITH PIPE SEGMENTS

Method of lining with pipe sections made of at least two pieces with both longitudinal and circumferential joints.

LINING WITH SPIRALLY WOUND PIPES

Method of lining with a profiled strip, spirally wound to form a continuous pipe after installation.

LIVE INSERTION

Method of installation of a liner whilst the product pipe remains in service.

LOCALISED REPAIR

Repair work on a pipe, particularly sewerage, for lengths less than the run between two adjacent access points.

LOCATOR

An electronic instrument used to determine the position and strength of electro- magnetic signals emitted from a transmitter sonde in the pilot head of a boring system, in an impact moling tool or from existing underground services which have been energised. Sometimes referred to as a Walkover System.

LOW LOAD METHOD

A pipe jacking method in which separate provision is made to carry the jacking load, the pipe being installed carrying little or none of the jacking force.

LUBRICATION

Means of reducing friction either around a pipe being jacked or a shaft being sunk into the ground.

Description of any operation which requires an operative to enter a pipe, duct or bore. The minimum size and other conditions for which this is permissible may be defined under health and safety legislation.

MANUAL MECHANICAL SHIELD

Open shield in which manpower is used to excavate the material but which has some steering capability.

MEASUREMENT WHILE DRILLING (MWD)

Instrumentation in a bore that provides continuous data simultaneously with drilling operations, usually transmitting to a display at or near the drilling rig.

Method of steerable remote control pipe jacking to install pipes of internal diameter less than that permissible for man-entry. In North America the term is used to describe remote control continuous pipe jacking in all diameters.

MIDI-RIG

Steerable surfaced launched drilling equipment for the installation of pipes, conduits and cables. Applied to intermediate sized drilling rigs used as either a small directional drilling machine or a large guided boring machine. Tracking of the drill string may be achieved by either a downhole survey tool or a locator.

Method of installing a pipeline by pulling a plough through the ground whilst a continuous length of pipe is fed into the top of the plough whilst a continuous length of pipe is fed into the top of the plough and buried from the tail.

First, usually steerable, pass of any boring operation which later required back- reaming or other enlargement. Most commonly applied to guided drilling, directional drilling and 2-pass microtunnelling systems.

PIPE BURSTING

Replacement method in which an existing pipe is broken by brittle fracture, using mechanically applied force from within. The pipe fragments are forced into the surrounding ground. At the same time a new pipe, of the same or larger diameter, is drawn in.

PIPE DISPLACEMENT

Term used in North America.

PIPE EATING

Replacement method, usually based on microtunnelling, in which a defective pipe is excavated together with the surrounding ground and a new pipe installed. The microtunnelling shield machine will usually need some crushing capability. The defective pipe may be filled with grout to improve steering performance. Alternatively, a proboscis device to seal the pipe in front of the shield may be used.

PIPE JACKING

Method for directly installing pipes behind a shield machine by hydraulic or other jacking from a drive shaft such that the pipes form a continuous string in the ground.

PIPE PULLING

Method of replacing small diameter pipes where a new product pipe is attached to the existing pipe which is then pulled out of the ground.

Non-steerable method of forming a bore by driving a steel casing, usually open-ended, with a percussive hammer from a drive pit. The soil may be removed by augering, jetting or compressed air. In appropriate ground conditions a closed casing may be used.

PIPE SPLITTING

Replacement method for breaking an existing pipe by longitudinal slitting. At the same time a new pipe of the same or larger diameter may be drawn in behind the splitting tool.

Method of repairing a brick sewer or manhole by the application of cement mortar where loss has occurred.

PRECONDITIONING WORK

That part of a project, usually before renovation work, which includes preparatory cleaning and internal inspection.

PREPARATORY CLEANING

Internal cleaning of pipelines, particularly sewers, prior to inspection, usually with water jetting and removal of material where appropriate.

PRODUCT PIPE

Permanent pipeline for operational use.

PULL-BACK

That part of a guided boring or directional drilling operation in which the drill string is pulled back through the bore to the entry pit or surface rig, usually installing the product pipe at the same time.

PULL-BACK FORCE

Tensile load applied to a drill string during pull-back. Guided boring and directional drilling rigs are generally rated by their maximum pull-back force.

Excavation into which trenchless technology equipment is driven and may be recovered during the installation or renovation of a product pipe, conduit or cable.

REHABILITATION

All methods for restoring or upgrading the performance of an existing pipeline system.

REINSTATEMENT

Method of backfilling, compaction and re-surfacing of any excavation order to restore the surface and underlying structure to enable it to perform its original function.

RENOVATION

Methods of rehabilitation in which all or part of the original fabric of a pipeline is incorporated and its current performance improved.

REPAIR

Rectification of local damage.

REPLACEMENT

Methods of rehabilitation of an existing pipeline system by the installation of a new system, either on or off the existing line, without incorporating the original fabric.

REROUNDING

Preparatory operation in which an expansion device is inserted into a distorted pipe to return it to a circular cross section. It is usually carried out prior to the insertion of a permanent liner or supporting band.

RESIN INJECTION

Method used in the localised repair of pipes, usually sewers, by injection into cracks, defects or cavities of a resin formulation which subsequently cures to prevent leakage and further deterioration.

ROBOT

Remote control device with closed circuit television (CCTV) monitoring, used mainly in localised repair work, such as cutting away obstructions, re-opening lateral connections, grinding and re-filling defective areas and injecting resin into cracks and cavities.

ROD PUSHING

Method of forming a pilot bore by driving a closed pipe head with rigid attachment from a launch pit into the soil which is displaced. Limited steering and monitoring capability may be provided, usually in conjunction with a locator.

Rotating drill pipe of larger diameter than the pilot drill and placed around it with its leading edge less far advanced. Its purpose is to provide stiffness to the drilling pipe in order to maintain steering control over long bores, to reduce friction between the drill string and the soil and to facilitate mud circulation. See Directional Drilling.

WATER JETTING

Method for the internal cleansing of pipelines using high pressure water jets.